From the report «Effect of Arbuscular Mycorrhizal Fungi on Heavy Metal Toxicity to Trifolium pratense in Soils Contaminated with Cd, Zn and Ni Salts», of I. VOROS, B. BIRO, T. TAKACS, K. KOVES-PECHY and K. BUSTAS, published at Agrokemia es Talajtan, Tom. 47. (1998) No. 1-4. 277.
Arbuscular endomycorthizal fungi (AMF) belong to the most common mycorrhizal type and are accepted as mutualistic symbionts of about 90% of the higher plants. In addition to macro- and micronutrient uptake, mycorrhiza may potentially affect the uptake of heavy metals, as a function of several factors, such as: the physico-chemical properties of the soil, soil fertility, pH, the host plants, the fungi involved and, above all, the concentration of the metals in the soil.
Root colonization with indigenous arbuscular mycorthizal fungi and their influence on plant growth and metal uptake were studied in a pot experiment with red clover (Trifoliwn pratense L.). Soil samples of pots originated from a long-term field experiment, where the calcareous chernozem soil was contaminated 4 years prior to the pot experiment by a single massive application of Cd, or Ni, or Zn sulphates at rates of 0, 30, 90 and 270 mg metal per kg soil. Red clover was grown for five months in the original metal-spiked soil, in gamma-irradiated sterilized, and in similarly sterilized but with mycorrhiza-free soil suspension re-inoculated soil samples. Fresh weight, biomass production, elemental content of the roots and shoots, and parameters of mycorrhizal infection were measured.
There was an approx. two-fold increase in biomass of red clover shoots in the presence of AMF symbioses, while root dry matter accumulation was similar in all treatments. In the presence of AMF, metal concentrations in roots and shoots were smaller (the latter to a greater extent) than metal concentrations in the non-mycorrhizal plants on sterilized soil. The results support the hypothesis that the presence of mycorrhizal symbiosis generally decreases metal transport into above ground plant parts. The infection frequency of AM fungi was only slightly influenced by the various metal rates, arbuscularity tended to be a more reliable indicator of harmful metal effects on higher plants.